Trump told the Post that he first thought of it after the Republican loss in the 2012 presidential election. Republicans were surprised at the loss, having thought their nominee Mitt Romney could have beat President Barack Obama, and Trump was considering how he could brand a run for president as a revival of the party and the country.

"As soon as the loss took place, I said, 'I'll tell you what, assuming I'm in a good position, assuming all of the things that you have to assume, which are many, I'm going to run next time,'" he told the Post. "And I sat back and I said, 'What would be a good expression? And I said, let's do this.'"

Trump outlined his thought process to the Post: "I said, 'We'll make America great.' And I had started off 'We Will Make America Great.' That was my first idea, but I didn't like it. And then all of a sudden it was going to be 'Make America Great.' But that didn't work because that was a slight to America because that means it was never great before. And it has been great before."

He continued: "So I said, 'Make America Great Again.' I said, 'That is so good.' I wrote it down. I went to my lawyers. I have a lot of lawyers in-house. We have many lawyers. I have got guys that handle this stuff. I said, 'See if you can have this registered and trademarked.'"

And indeed, just days after Romney's loss, Trump signed an application to trademark the phrase.

Trump, however, is not the first to use the slogan — President Ronald Reagan prominently featured the words on his campaign materials. Trump said he didn't know until about a year ago that Reagan had also used the phrase.

Trump told the Post what the slogan means to him.

"I felt that jobs were hurting," he said. "I looked at the many types of illness our country had, and whether it's at the border, whether it's security, whether it's law and order or lack of law and order. Then, of course, you get to trade, and I said to myself, 'What would be good?' I was sitting at my desk, where I am right now, and I said, 'Make America Great Again.'"